The "Benefits" of Distractibility: Mechanisms Underlying Increased Stroop Effects in Schizophrenia

Abstract

Recent studies of selective attention in schizophrenia patients suggest a particular pattern of single-trial Stroop performance: increased facilitation but not interference in reaction times (RTs), combined with increased error interference. Our Stroop task analysis suggests that this pattern can be explained by a selective attention deficit if one accounts for (1) performance in the congruent condition; (2) the nature of the neutral stimulus; (3) the relationship between accuracy and RT; and (4) response set effects. To test these hypotheses, we examined Stroop performance in 40 DSM-IV schizophrenia patients and 20 healthy control subjects, using a range of neutral stimuli (color patches, noncolor words, color words not in the response set). The findings confirmed several of our predictions and the results were consistent with the hypothesis that abnormal Stroop performance in schizophrenia reflects a failure to adequately attend to the task-appropriate stimulus dimension (color). This inattention affects both the congruent and incongruent conditions and multiple points in the information processing pathway.

Acute Serotonin and Dopamine Depletion Improves Attentional Control: Findings from the Stroop Task

“…Following the task used by Barch et al (1999a), we used a single trial version of the Stroop task consisting of 96 trials; with 24 (25%) congruent trials, 24 (25%) incongruent trials, and 48 (50%) neutral trials. Each trial consisted of a stimulus printed in one of four colors: red, green, blue, or purple.…”

“…These neutral words were from a single semantic category in order to eliminate semantic confounds (MacLeod, 1991), and matched the response set color words in terms of number of letters and frequency of occurrence in the English language (Francis and Kucera, 1982). The use of these animal words as the neutral stimuli, rather than patches of color, was due to previous research suggesting that these neutral stimuli are more likely to produce a Stroop facilitation effect in healthy participants (Barch and Carter, 2005;Barch et al, 1999aBarch et al, , 2004.…”

“…Experimentally, this deficit is most evident when patients are administered paradigms such as the Stroop Color-Word Interference task (Barch and Carter, 2005;Barch et al, 1999aBarch et al, , b, 2004Braver et al, 1999;Carter et al, 1992;Chen et al, 2001;Cohen et al, 1990;Henik and Salo, 2004). The Stroop task is a wellestablished measure of attentional control and response inhibition, in which participants are presented with words printed in different ink colors and are told to name the print color and to ignore the stimulus word.…”

“…This reaction time difference is referred to as Stroop interference and shows high reproducibility and robustness within and across individuals (MacLeod, 1991). In contrast, a less studied phenomenon, referred to as Stroop facilitation, occurs when participants are faster to respond to stimuli when the color is congruent with the semantic meaning of the word, than to neutral stimuli such as patches of color (Barch et al, 1999a). However, facilitation is considered to be a somewhat weaker phenomenon than interference (MacLeod, 1991).…”

“…However, facilitation is considered to be a somewhat weaker phenomenon than interference (MacLeod, 1991). Research suggests that patients with schizophrenia exhibit increased facilitation, an increased number of errors and increased reaction times to all stimuli, but have no difference in interference, when compared to healthy control participants on the single-trial version of the Stroop task (Barch et al, 1999a(Barch et al, , b, 2004Carter et al, 1992;Chen et al, 2001;Henik et al, 2002;Nordahl et al, 2001;Perlstein et al, 1998;Taylor et al, 1996). These findings are thought to be as a result of a specific failure in contextual processing, whereby patients have difficulty implementing and/or maintaining a representation of the task goals over time (Barch and Carter, 2005;Barch et al, 1999a, b).…”